When using electro-hydraulics in machines being provided with buckets, for example loaders, earthmovers and power shovels, normally a control signal being generated by an operator via a control member is used for the bucket control. Thereby, a computer or a control unit is arranged for manipulating the signal and ensuring smooth operation in normal conditions. Therefore, when a valve being used for the bucket control or the like is activated, the acceleration and deceleration of the bucket normally are reduced in order to give smooth starts and stops, improved stability, less fatigue stress on the mechanical structure and on the hydraulics. This causes a problem, however, when the bucket is to be cleaned by means of shaking.
In conventional machines, the operator usually moves the bucket rapidly back and forth in order to shake dirt out of the bucket in this way. This movement of the bucket is triggered by the operator moving a control lever rapidly back and forth, normally the regular bucket tilt lever.
From U.S. patent application US 2002/0065575, Francis et al., it is known with a bucket shakeout mechanism for electro-hydraulic machines. According to US 2002/0065575, the bucket shakeout mechanism includes a mode control module, being stored on a memory device and comprising a smooth mode module and an abrupt mode module. The abrupt mode module can be activated by means of a special manipulation of a control lever or a joystick controller. When activating the abrupt mode module, the control lever characteristics are changed, so that a given control lever displacement results in another opening response of the hydraulic valve being used for the shaking than what is the case with the corresponding control lever displacement when the smooth mode module is activated. It may also be looked upon as the signal characteristics being changed depending on the selected operating mode module.
Accordingly, according to the above-described publications, a given set of control parameters is changed when switching from one operating mode module to another. In this case, the change consists in the opening degree value of the hydraulic valve being increased for a given control lever displacement value, or that the maximum opening degree of the hydraulic valve is increased when switching from smooth mode operation to abrupt mode operation.